Commonly-owned U.S. patent application Ser. No. 08/152,812 filed Nov. 16, 1993 (now U.S. Pat. No. 4,576,211, issued Dec. 19, 1995), and its counterpart commonly-owned copending "divisional" U.S. patent applications Ser. Nos. 08/457,479 filed Jun. 1, 1995 (status: pending) and 08/570,230 filed Dec. 11, 1995 (status: pending), disclose methods for making resilient interconnection elements (spring contact elements) for microelectronics applications involving mounting an end of a flexible elongate core element (e.g., wire "stem" or "skeleton") to a terminal on an electronic component, coating the flexible core element and adjacent surface of the terminal with a "shell" of one or more materials having a predetermined combination of thickness, yield strength and elastic modulus to ensure predetermined force-to-deflection characteristics of the resulting spring contacts. Exemplary materials for the core element include gold. Exemplary materials for the coating include nickel and its alloys. The resulting spring contact element is suitably used to effect pressure, or demountable, connections between two or more electronic components, including semiconductor devices.
Commonly-owned, copending U.S. patent application Ser. No. 08/340,144 filed Nov. 15, 1994 (status: pending) and its corresponding PCT Patent Application No. PCT/US94/13373 filed Nov. 16, 1994 (published as WO95/14314 May 26, 1995, pending), both by KHANDROS and MATHIEU, disclose a number of applications for the aforementioned spring contact elements, and also discloses techniques for fabricating contact pads (contact tip structures) at the ends of the spring contact elements.
Commonly-owned, copending U.S. patent application Ser. No. 08/452,255 filed May 26, 1995 (status: pending) and its corresponding PCT Patent Application No. PCT/US95/14909 filed Nov. 13, 1995 (published as WO96/17278 Jun. 6, 1996, pending) disclose additional techniques and metallurgies for fabricating spring contact elements as composite interconnection structures and for fabricating and mounting contact tip structures to the free ends (tips) of the composite interconnection elements.
Commonly-owned, copending U.S. patent application Ser. No. 08/819,464 filed Mar. 17, 1997 (status: pending) and its counterpart PCT Patent Application No. US97/08606 filed May 15, 1997 (status: pending) disclose a technique whereby a plurality of elongate tip structures having different lengths than one another can be arranged so that their outer ends are disposed at a greater pitch than their inner ends. Their inner, "contact" ends may be collinear with one another, for effecting connections to electronic components having terminals disposed along a line, such as a centerline of the component. Additional contact tip structure methods and apparatus are disclosed in these patent commonly-owned applications.
The present invention addresses and is particularly well-suited to making interconnections to modern microelectronic devices (components) having their terminals (bond pads) disposed at a fine-pitch. As used herein, the term "fine-pitch" refers to microelectronic devices that have their terminals disposed at a spacing of less than 5 mils, such as 2.5 mils or 65 .mu.m. As will be evident from the description that follows, this is preferably achieved by taking advantage of the close tolerances that readily can be realized by using lithographic rather than mechanical techniques to fabricate the contact elements.